A Christmas light bulb set typically comprises a miniature light bulb seated in a bulb holder and enclosed in a socket body. The bulb holder and socket body are made of plastic materials and usually interconnected by press fit. The outer diameter of the bulb holder is slightly larger than the inner diameter of the socket body in order to attain a tight fit. However it brings difficulties in manufacturing. If the holder is too large, it is hard to insert the holder into a socket body. On the other hand, if the holder is smaller than the required, the holder will easily slip out of a socket body. Thus such a securing mechanism causes much trouble in the field.
In view of the above problem, the primary object of the invention is to provide an engaging mechanism that is used in a miniature light bulb socket and by which a light bulb holder can be securely combined with a socket body without a separation possibility. Now the features and advantages of the present invention will be detailed below with reference to the accompanying drawings.